Candles release carbon and metal particles which could raise the risk of heart and lung problems, a study has warned.

一项研究提醒，蜡烛释放的碳和金属颗粒会增加患心肺疾病的风险。

The scented candle market is worth £90million in Britain and they have become a favourite gift, used to freshen living rooms or add a gentle glow to bathtimes.

But the US study found burning candles of any type in the home increases particles of pollution by 30 percent - and opening doors and windows does very little to help.

Frying and burning food have the same effect. So lighting a scented candle after burning the dinner might only make matters worse.

The US researchers scanned 300 family homes for pollution including fine particles between 0.5 and 2.5 micrometres in size – a range that includes dust, fungal spores and vehicle emissions.

Smoking at home was found to be the major source of airborne pollution. But burning candles and frying food with oil raised levels by almost a third.

Air pollution expert Professor Ian Colbeck, from the University of Essex. said he believed the risk of health problems was the same for scented and unscented candles.

The US study, published in the journal PLOS ONE, concluded that indoor pollution was even worse for big families living in small houses.